Shredding and mixing machine



Dec. 31, 1935. sc r AL 2,026,049

SHREDDING AND MIXING MACHINE Filed May 2, 1934 :U.O 0 33:3 I242Zlwwntoz; ALBERT .LAS ERNST STROMER exceeded without spoiling thematerial.

Patented Dec. 31, 1935 UNITED STATES PATENT OFFICE SHREDDING AND MDHNGMACHINE York Application May 2, 1934,'Serial No. 723,491 In GermanyAugust 19, 1933 1 Claim.

This invention has to do with shredding and mixing machines which areused for breaking down, mixing, and dissolving materials such as wood,cotton, or scrap-paper cellulose and the like, for the manufacture ofrayon.

Heretofore an operation of this nature usually has been performed in onestage in a single large mixer of the well-known type having a pair ofblades rotating toward each other on parallel axes in semi-cylindricalhalves of the trough bottom, co-operating with a ridge or saddleseparating the halves. In the treatment of raw cellulose in machines ofthis type certain natural limitations are encountered. First, a largecapacity mixer of this type has, in proportion to its volume, arelatively small watercooled sm'face area. A great deal of heat 'isgenerated by the shredding operation, and cellulose batches as well asmixtures of other materials are variously limited as to the temperatureto which they may be heated without spoiling the product. Therefore, thepower input and consequently the rate or speed of operation has beenlimited heretofore by the ability of the cooling means to carry away theheat created by working the batch.

Mechanical limitations also affect the rate of output when the initialdisintegration of large pieces and the final reduction of the mass tosmall particles are performed in a single machine. Rather large workingclearances between the blades, the trough walls, and the I saddle arerequired for the most effective breaking down of large pieces. If theblades are provided with cutting nd tearing teeth, as is desirable forworking fibrous material, the initial disintegration of large pieces-isperformed best with relatively large, coarse teeth. Also, for the mosteflicient breaking up of large pieces, a slow speed of operation of theblades is necessary, due to the greatpower required and the aforesaidtemperature limit which cannot be The final comminution of themoderately reduced material can be performed best by blades having aslight clearance from the co-operative trough surfaces, having fineshredding teeth, if any, and operating at high speed.

Necessarily, therefore, a single machine used for the entire operationmust be a compromise between those dimensions and operatingcharacteristics of the working elements best suited for the initial andfinal stages of the operation. It is necessary also to providespeed-changing means in the driving mechanism for the blades so thatdiiierent working speeds are available for the various stages in thetreatment of each batch.

Our invention overcomes the disadvantages set forth above and provides amachine which 5 will shred and disintegrate large quantities of materialin much less time than could the previous single machines, therebyreducing the overhead cost per unit batch.

The invention by which these desired objects are attained consists of amixing machine having a plurality of pairs of blades mounted on parallelaxes, each blade within its co-axial semi-cylindrical trough, aridge-shaped saddle between each pair of troughs, and a removablepartition between each two adjacent pairs of troughs, so that in eiiecta series of small mixers are housed in a single machine. Each pair ofblades is adapted to perform most eiiiciently its share of theprogressive complete reduction of the material.-

In a two-compartment machine according to the invention, one subdivisionof the mixer has blades ,designed and/or driven at the moderate speedbest for initially breaking down large pieces of raw material andeffecting half the ultimate reduction in their size. This section of themixer is arranged so that the rotating blades discharge the partlyworked batch from the first into the second section of the machine whenthe partition between the two is removed. In the second trough theblades have working clearances and shredding teeth fine enough best toreduce the preliminarily shredded particles to their ultimate fineness.This second set 'of 85 blades is driven at high speed best suited forthe.. operation.

By reducing the diameter of the four blades and their trough sections ascompared with the single pair of blades previously used, the surface 40area of the machine in proportion to its ca,- pacity is increased.v Thusmore effective cooling may be maintained, permitting the blades to bedriven at increased speed, thereby reducing the overall working time fora batch of 4 material.

A further advantage of the improved machine is that a more nearlycontinuous output of finished material is obtained, since a morefrequent discharge of smaller batches is obtained, that is, disregardingthe permissible increased operating speed, batches of half the size willbe discharged twice as fast as in thec'ase of a mixer of the samecapacity employing one pair of blades.

In operation a batch of raw material is first placed in the compartmentin which the slowspeed blades effect the initial coarse reduction of theparticles. When this half of the operation is completed, the partitionis removed, and the blades kick the initially sized material into thesecond sub-division of the machine, in which the other pair of bladesoperate. The partition is then replaced. A fresh batch of raw materialis placed in the first compartment, and the semi-sized material isfinely shredded and masticated by the second pair of blades, which areclosely fitted and driven at the high speed suited for the purpose.Those two stages of the operation proceed simultaneously until thematerial in the second compartment has been completely disintegrated andmixed, when it is discharged from the machine in known manner. Thedischarge openings are closed, the partition is removed, the partlysized material in the first compartment is transferred into the secondcompartment of the machine, the partition is replaced, and a fresh batchof raw material is added.

Having set forth the general nature and mode of operation of myinvention I will now describe the construction and operation of apreferred form of machine embodying its features, having reference tothe accompanyingdrawing, in which Fig. 1 is a sectional side elevation.

Fig. 2 is a sectional side elevationof a modification of the machineshown in Fig. 1.

Referring to Fig. 1, a mixing trough I, water- ;Iacketedfor cooling, hasan inclined bottom provided with four semi-cylindrical trough sections!of conventional form. Trough l is divided by a removable partition 3into two compartments A, B. In the mixing compartment A a pair of blades4, 5 are mounted for rotation,

each blade in a semi-cylindrical trough section 2.

Blades 4 and 5 are provided with driving means, not shown, of knownform.

The blades 4, 5 are so dimensioned and are provided at their workingedges with shredding teeth appropriately shaped and of a size bestadapted to break down large pieces of raw material into pieces ofmoderate size. The blades are driven toward each other as indicated bythe arrows at a slow speed which will cause them to perform theirfunction without excessively heating the material.

In the second finishing compartment B a pair of blades 6, I are mountedsimilarly to those in section A, but their working edges, the cuttingteeth thereon, their working clearances from the trough walls, and thehigh operating speed are all selected to disintegrate and comminute thepreliminarily sized particles of raw material and to complete dissolvingthe batch most effectively and rapidly.

Discharge from section B of the trough is effectedthrough a horizontallyhinged swinging door 8 in the lbwer wall of the mixer, which is providedwith a clamping latch 9 of known form. The operation of the machine isas follows:

The raw ingredients of the first batch are charged into section A of thetrough. Blades 4, 5 operate on it at slow speed until all the largepieces are broken down to the desired maximum size. Preferably one-halfof the overall reduction of the batch is performed in section A. Thepartition 3 is then raised from the position in which it is shown, andthe material flows and is kicked by blade 4 over into compartment B. Thepartition 3 is lowered, a fresh batch of ner of the machine of Fig. 1.

raw material is put into section A and the machine is operated until thebatch in section B is ready for discharge. The discharge door 8 is thenunlocked and swung open and the material is expelled by blade 6 in theusual manner. The gate 8 is then closed, the partition 3 is raised, andthe material which has been treated in section A flows and isdriven byblades 4, 5 into section B for the completion of its treatment; Thepartition is replaced, a fresh batch of raw material is put into sectionA, and the cycle of operations is repeated.

Fig. 2 shows a modification of the invention in which the axes of thetwo pairs of blades of the compartment bottoms join in an ele-- vatedridge. By this construction the overall height and the weight of themachine is reduced as compared with a machine of the same capacityaccording to Fig. 1.

Another advantage of, this machine is its adaptability and flexibilityin service. Either compartment can be used alone as a mixer foreconomically preparing small batches of material in conventional manner.The other compartment and its blades can remain idle, or can be used atthe same time to treat another mixture. Discharge doors for eachcompartment are provided in both end walls of the machine at the lowends of the compartment bottoms. whence the quickest and most completedischarge of mixed material is effected.

Referring to the drawing, the trough la is divided into two mixingcompartments C and D, the bottoms of each comprising two semicylindricalparallel trough sections 241 of known form, the axes of each pair ofsections lying in planes which are inclined upwardly from the ends ofthe trough la toward its middle. A removable vertical partition 3aseparates the two compartments C and D. Blades 4a. and 5a are rotatablymounted in the trough sections 2a of compartment C, blades 6a and 1a incompartment D. Discharge doors 8a and 8b are are provided in the outerwalls of both compartments for use when the sections C and D areemployed as individual small mixers.

Only one of the discharge doors, as 81), is used when the machine isoperated in the man- For example, the raw material is placed incompartment C where it is partly broken down, the partition 3a is thenremoved and the batch passes into compartment D for its final shreddingwhile a second batch of fresh material is being treated in compartmentC. The completely reduced ma-'- terial is discharged from compartment Dthrough door 8b. 1 l

Another feature of the machine is that the operating sequence of one of.the two mixing compartments may be reversed, is desired. 'The initialbreaking down of a batch ,can be done in compartment D, the finalshredding in com partment C, and the batch discharged through door 8a.To adapt the machinev to these variousl modes of use the two pairs ofblades or rotorsjq, 5a, 6a,;1care preferably identical as to the size oftheir shreddingteeth, if any, and -'have like clearances from theirrespective co ,-opera tive trough bottoms and saddles. vThe fundamentalprinciple of the invention is retained, however,

not shown.

Either trough section may be used for the first stage of the mixingprocess, if desired. In this event both pairs of blades will be alike indesign and working clearances, but whichever pair performs the firstpart of the mixing process will be driven slowly and the other pair willbe driven at a higher speed.

To make this reversible use of the machine possible, two similardischarge doors 8a, 8b are provided, one at each end of the machine,pe'rmitting a discharge from either end of the trough sub-division. Inoperation of course only one of these doors will be employed at a giventime.

Since the compartments are at the same level, with an elevated ridgebetween them, complete transfer of a preliminarily treated batch, asfrom section into section D, may not be possible. Only a portion, say,half or two thirds, depending upon the size of the batch, will naturallypass from section C to section D when partition 30 is raised. This maynot be objectionable in most cases, fresh raw material being added tothe balance of the material remaining in the first section C afterthepartition So has been replaced. However, a more complete transfer may beefiected by providing means for reversing the direction of rotation ofone pair of blades, for example, 6a and la, during the discharge ofmaterial from section 0 into section D, so that the bulk of the materialcoming into compartment D will be moved to the left against the outerwall.

In practice the complete discharge of each batch, preliminarily treatedin section C, into section D need not occur to obtain substantialbenefits of the invention, since large pieces of raw material will'bebroken down in, say, section C of the machine, in which the blades aredriven at a speed best suited to the task, and the final shredding ofthe partly reduced particles will be done in the other section D,wherein the blades can be driven at high speed for speedy and thoroughcompletion of the disintegration and mixing of the material.

* In the machines shown there is a tendency for the bulk of the materialto flow into the lower semi-cylindrical trough, so that the upper of thepair of blades does not work as effectively as its lower mate. Toovercome this difficulty by more evenly distributing the load over bothblades, the end wall of the machine adjacent a lower blade may beinclined in- 5 wardly toward its top. This construction is illustratedby dotted lines.

Experimentation has shown that increased cooling surface in proportionto the capacity of the machine is made possible by our invention.

For instance a 7000 liter, two-bladed machine has 11.8- square meters ofcooling surface, or one square meter of cooling surface for each 732liters capacity. In a four bladed machine,

as shown and described, having a capacity of 7000 liters there are 14square meters of cooling surface, or one square meter for 265 literscapacity. In other words, the ratio of cooling surface to capacity hasbeen increased 2 /2 times. Therefore, greater power-input to the rotorsis permissible and greater output per hour is secured from a machine ofgiven size.

Simplicity in driving mechanism and ease of operation is provided by theinvention- Single machines previously used for shredding operations haverequired the provision of speedchanging means in the gear trains drivingthe blades, so that they could be operated .at low speed upon the freshmaterial and then speeded up for the latter part of the operation. Thema-' chine attendant thus had to change the blade speed twice for eachbatch turned out. In the present invention. each set of blades operatesat, a constant speed and may be directly driven,

eliminating driving parts and reducing 'the amount of attendancerequired.

Having thus described our invention, what we claim and desire to secureby Letters Patent is:

In a shredding and mixing machine, two mix- I ing compartments side byside, the bottom of 40 each compartment having parallel intersectingsemi-cylindrical trough sections whose axial planes are inclinedupwardly from the end walls of the machine toward its middle, a rotormounted in each trough section and coaxially therewith, power-actuatedmeans for driving the rotors of adjacent compartments at differentspeeds, a removable partition between said compartments, and a dischargedoor in each end wall of the machine opening into the lower part of eachof said compartments.

' ALBERT LASCH.

ERNST s'mijrma.

